Editor chasing almost certain voting system is shocked (9)
I believe the answer is:
surprised
'shocked' is the definition.
(I've seen this before)
'editor chasing almost certain voting system is' is the wordplay.
'editor' becomes 'ed'.
'chasing' is a charade indicator (letters next to each other).
'almost' means to remove the last letter (most of the word but not all of it).
'certain' becomes 'sure' ('sure' can be a synonym of 'certain').
'voting system' becomes 'pr' (I've seen this in other clues).
'sure' with its last letter removed is 'sur'.
'sur'+'pr'+'is'='surpris'
'ed' after 'surpris' is 'SURPRISED'.
(Other definitions for surprised that I've seen before include "Startled" , "Took unawares" , "Lost for words" , "Mildly astonished" , "hit for six" .)